There are many types of imaging devices that are used to provide a record of captured images. Data may sometimes be extracted from the captured images. Exemplary data may be text from documents, measurable parameters in the image, etc.
Optical reading devices may be one type of imaging device, and typically read data represented by symbols. For instance a bar code symbol is an array of rectangular bars and spaces that are arranged in a specific way to represent elements of data in machine readable form. Optical reading devices typically transmit light onto a symbol and receive light reflected off of the symbol. The received light is interpreted by an image processor to extract the data represented by the symbol.
One-dimensional (1D) optical bar code readers are characterized by reading data that is encoded along a single axis, in the widths of bars and spaces, so that such symbols can be read from a single scan along that axis, provided that the symbol is imaged with a sufficiently high resolution along that axis.
In order to allow the encoding of larger amounts of data in a single bar code symbol, a number of 1D stacked bar code symbologies have been developed which partition encoded data into multiple rows, each including a respective 1D bar code pattern, all or most all of which must be scanned and decoded, then linked together to form a complete message. Scanning still requires relatively high resolution in one dimension only, but multiple linear scans are needed to read the whole symbol.
A class of bar code symbologies known as two dimensional (2D) matrix symbologies have been developed which offer orientation-free scanning and greater data densities and capacities than 1D symbologies. 2D matrix codes encode data as dark or light data elements within a regular polygonal matrix, accompanied by graphical finder, orientation and reference structures. When scanning 2D matrix codes, the horizontal and vertical relationships of data elements are recorded with about equal resolution.
Often times a bar code reader may be portable and wireless in nature thereby providing added flexibility. In these circumstances, such portable bar code readers form part of a wireless network in which data collected within the terminals is communicated to a host computer situated on a hardwired backbone via a wireless link. For example, the portable bar code readers may include a radio or optical transceiver for communicating with a host computer via a base station.
Efforts regarding such systems have led to continuing developments to improve their versatility, practicality and efficiency.